Our body needs energy to function. To create energy fuel is needed. Food is the fuel for our bodies. And here is the start point of every discussion on this matter: whether the food we provide for our bodies is well proportioned or not results in our health condition. In the following we will draw some lines of nutrition information to understand some basic principles.

Quality feeding must provide a specific proportion of nutrients to respond to the needs of our body. Nutrients are obtained when foods are digested and absorbed. Food nutrients: protein, fat, carbohydrate, vitamins, minerals, water.

Lately it was agreed upon the fact that one of the most important factors affecting health and body weight is the Glycemic Index(GI) of food. GI is a classification of carbohydrates on a scale from 0 to 100 according to the level to which they raise blood sugar levels after eating. This theory comes to complete the traditional one according to which, for weight to remain stable, the energy intake must equal the consumed energy.

Energy

Energy expenditure consists of:

• the amount of consumed energy for burning calories while at rest (REE) — 60-70% of the energy output,
• the energy used for physical activity,
• the energy spent for metabolizing food and maintaining the body temperature (especially for cold-induced thermogenesis) => only a small amount of energy is consumed.

Energy is measured in calories or joules. Although calories apply to anything containing energy, they are often associated with food and dieting. Talking about food calories we refer to the amount of potential energy that a food contains. On food packages the mentioned amount of calories refers in fact to kilocalories (1 kcal=1,000 cal). Sometimes, the word “Calorie” is capitalized to show the difference but most times it is not.

Each person's calories necessity is influenced by age, gender and activity; it increases with age up to adolescence and then a decrease follows. Children's needs increase in the first year of life from around 520 kcal/day (varying with gender) to around 1,000 kcal/day, reaching at preschool age around 1,600 kcal/day. By the age of adolescence, their energetic needs reach around 2,800kcal/day for boys — the same as for active men and very active women — and 2,200kcal/day for girls — the same as for active women, and many sedentary men; women who are pregnant or breastfeeding may need somewhat more. For many sedentary women and some older adults around 1,700kcal/day is about right.

A very good source of information on energetic needs is The food guide pyramid.

Nutrients

Some nutrients are energy-providing. Varying with particular needs, a good proportion of energy-generator nutrients must be maintained in a diet in order to keep the balance and the body weight constant.

Besides providing energy, nutrients are also needed for the body to build and maintain tissues, hormones, etc. and to regulate the body functions of the blood, heart, brain, liver etc.

Main Food Groups

A healthy diet is one that supplies enough nutrients in the right proportion. The human body needs over 40 different nutrients each day. A diet containing a varied range of nutrients can be achieved by eating a variety of foods from all main food groups:

Grain Products

Whole grain and enriched products are advised (bread, cereal, rice, and pasta). According to the traditional recommendations, this group of foods was to prevail in our diet. This is the group that contains the biggest amount of carbohydrates (together with the sweets) and recent studies have settled the inconveniences of a diet based on high carbs level. However they should not be entirely removed from our foods list but should be eaten in moderation. The proportion is changed from the traditional recommendations of 5 to 6 servings a day to 2-3 servings each day.

Vegetables and Fruits

Dark green vegetables and orange fruit and vegetables are recommended. Fruit — two to four servings each day. Vegetables — three to five servings each day.

Dairy (milk, cheese)

Low fat products are recommended. Two to three servings each day. The low carbs foods in this group should be consumed up to 4-5 servings a day.

Meat and Alternatives

Lean meat, poultry and fish, as well as dried peas, beans and lentils are recommended. The traditional recommendations were two to three servings each day. In the light of the new nutrition approach, the low carbohydrate content is a point in favour of larger quantities, up to 5 servings a day.

Fats, Oils and Sweets

Fats and oils are needed for a good functioning of the body but only good fats — unsaturated ones are recommended. Sweets are to be used sparingly — in small amounts and not very often.

Specifications for the status of the main food groups in the light of the South Beach Diet can be found in the article The Main Food Groups and the Diet

Here is some orientative data regarding the amount on one serving(the amount may vary with individual necessities but must not surpass reasonable limits):

Everyone needs the same nutrients but in specific proportions, varying with individual needs, which are determined by particular factors such as age, gender, size, activity level and general health.